Cathode ray tube



May l5, 1945. K.l oHL 2,375,815

' cATHoDE RAY TUBE File@ Nov. 3, 1941 UUUU Patented May i5, 1945 CATHODE RAY TUBE Klemens Ohl, Stockdorf, near Munich. Germany; vested in the Alien Property Custodian Application November 3, 1941, Serial No. 417,655 In Germany January 22, 1940 6 Claims. (Cl. Z50-162) The inventionrelates to cathode ray tubes, especially for television or oscillographic purposes, and more particularly of the type provided with a control electrode for influencing the intensity of the cathode ray beam.

Tubes of the kind heretofore used suffer from several disadvantages. Usually, the control electrode has the shape of a cylinder surrounding the cathode nearly completely and closed at its end by an apertured diaphragm. In this embodiment oi the known type of cathode ray tubes, the capacity between the control electrode and the surrounding elements, especially the cathode,

is by far too large for enabling the tube to be operated at high oscillation frequencies.

In these and other embodiments of known tubes, the cathode further is often supported by a centering member closely fitting round the cathode body. By this arrangement a considerable heat dissipation is involved and the requirement of heating power accordingly is comparatively high.

It is an object of the invention to provide a cathode ray tube wherein the capacity between the control electrode and the neighbouring elements is minimised.

It is another object of the invention to reduce the heat dissipation from the cathode body.

It is a further object of the invention to facilitate the manufacture of the electrode assembly and to shorten the axial length of the tube.

According to the invention, the control electrode has the shape of a small apertured disc or diaphragm and is mounted in a central recess of a ring-shaped centering member of insulating material which is closely tted in and supported by the one end of a cylindrical electrode, while the cathode projects from the outside into the centering member to face the control electrode.

The invention will be better understood with the aid of and further features of the invention will be apparent from the following more detailed description and accompanying drawing, which in a purely diagrammatic fashion and by way of example illustrates a cross-section of the socket portion and o'f the cathode ray producing system of a tube according to the invention.

In the drawing, l is the equipotential body of a cathode bearing the emissive substance 2 at its front surface and adapted to be indirectly heated by the filament `3. The cathode body I is carried by a supporting member 4 which is fastened to a ring-shaped member 6, preferably by means of a glass bead 5. The surface of the joint between the cathode body l and the supporting member Il is made as small as possible in order to reduce the heat conduction from the cathode. For the same purpose the member li may be shaped as a rod or wire of comparatively small cross-section.

rfhe member 6 may consist of ceramic material, pressed glass, or preferably, burnt steatite. The control electrode indicated by l has the shape of a small apertured disc or diaphragmand is mounted in a central recess of the .centering member 6.

The opening of the member E, at the upper end of this element and along the greater part of its axial length, is preferably `cylindrical and has a diameter which is considerably larger than that of the cathode body i. At the ibase of the centering member the diameter of its opening is substantially equal to that of the cathode body,

so that but a small play is -left between the centering member 6 and the cathode Ibody l, just sufficient for pushing the cathode body through.

Preferably, the opening of the annular member i5 has a narrowing towards its lower' end, and the narrow portion of the member 6 is limited to a very short part of its axial length.

By this means the heat conduction from the catlfiode to the centering member is minimised, and stray electrons can hardly manage to penetrate into the discharge space.

The position of the control diaphragm l is further secured by a lead-wire 8 passing through a slit of the centering member Ei. Preferably, the conductor 8 is fastened to the member. 8 by means of a further glass bead 9.

The centering member 6 is closely tted in the lower end of a cylindrical electrode it and may be secured to this electrode by a glass bead (not shown in the drawing) connecting the two elements.

It is advantageous to use the member 6 at thesame time as a spacing means. This feature can :be realized in a particularly simple manner when, as it is usual, the control electrode l, in the direction of the electron movement, is followed by a first anode diaphragm Il mounted within the cylinder lli. In this case it is merely necessary to shape the member 6 in such a way that the correct position of the control electrode 'l and the diaphragm li with respect to one another is obtained, when the member 6 is just closely adjoining to the diaphragm Il. In more general cases the member E may be provided with a nange or shoulder to fix its correct position with respect to the cylindrical element I0.

'Ihe electrode assembly as described above is time can be used as lead-in conductors.

preferably supported by and fixed to supporting rods I4 and I5 as indicated in the drawing. In a preferred embodiment of the invention the supporting rods I4 and I5 are directly embedded in the socket portion I2 of the tube envelope which is formed by a base plate consisting of pressed glass. The base plate I2 may be Sealed to the bulb portion I3 of the tube envelope by means of a glass flux I9. Further supporting rods pressed in the glass base may be provided for supporting other elements of the electrode system, which are not villustrated in the drawing.

Preferably, at least a part of the supporting rods passes through the base disc I2 and is provided at the ends outwardly projecting from Vthe base disc with socket pins or similar contact pieces I6 so that the supporting rods at the same In the example illustrated by the drawing, the supporting rod I4 is at the same time the lead-in conductor for the cylindrical electrode I0. In this case, insulation between the cathode I and the electrode I4 may be required, which can easily be obtained, for example by making the supporting member III at least partly of insulating material. The supporting rod I5 is used as the leadin conductor for the control potentials.

Additional lead-inrods .I1 are.provided if necessary, The .lead-in rods are also directly embedded and pressed in the glass flux of the base plate I2. As shown in the drawing, the lead-in rods I'I serve for supplying the cathode filament 3 with the heating current. Intermediate conductive strips I8, `preferably consisting of elastic metal, may be provided.

Preferably, the materials of the lead-in or supporting rods and the glass base I2 are selected to have the same heat expansion coencient. Likewise, care should be taken'that the heat expansion coeicients of other metallic elements, for example the cathode I, the control electrode 1, the cylinder I0, and the diaphragm II, are substantially equal to the heat expansion coeiiicients of the adjoining insulating elements, for example the centering member 6.

It may be stressed once Vmore that the drawing is purely diagrammatic and not on scale. Especially the distance between the cathode body I and the base plate I2 is considerably smaller and can be reduced in practical embodiments of the tube according to the invention to a few millimetres. By the way a remarkably short length of the tube system is obtained.

In the manufacture of a tube according to the invention it is advantageous to proceed as follows: With the aid of a spacing and centering means the cathode body I and the control electrode 'I which are already provided with their supporting members 4 and 8, are brought into their correct position with respect to the centering member 6. The assembly is secured by means of the glass beads 5 and 9 and the auxiliary spacing and centering means are removed. This structural unit is slipped into the cylinder I0. Hereafter the heating element 3 may be introduced into the cathode bodyvI.

The lead-in and supporting rods are directly embedded in the molten glass ux of the base disc I2 during the pressing process of the latter.

The electrode assembly is mounted on the base member and the single elements are xed to their supports and connected to their lead-in conductors, preferably by soldering in vacuo.

The base portion carrying the electrode system is then sealed to the glass envelope by means of the glass flux I9 which preferably consists of a molten glass powder applied to the bulb portion I3.

Further steps of the process which are not mentioned in the above, for example degassing and evacuating the tube, may be carried out in any known fashion. Further, it need not be mentioned that the complete electrode system of the tube may comprise electrodes, for example wall coatings and similar elements, which are not supported by and conducted through the base portion of the tube.

Although in this specification and the accompanying drawing certain specific constructions and methods `are described, the invention is not limited to the details kset forth. Various changes and modifications are possible within the scope of the invention as dened in the specification, drawing and the appended claims.

I claim:

1. A cathode ray tube comprising a cylindrical electrode, a ring-shaped centering member of insulating material, closely tted in and supported by the one end of said cylindrical electrode, a disc-shaped control electrode mounted in a central recess of said centering member at the side of said centering member facing the interior of said cylindrical electrode, and fm equipotential cathode projecting from the outside into said centering member to face said control electrode, said cathode being carried by `e supporting member fastened to said centering member by means of a glass bead.

2. A cathode ray tube comprising a cylindrical electrode, a ring-shaped centering member oi insulating material, closely fitted in and supported by the one end of said cylindrical electrode, a disc-shaped control electrode mounted in a central recess of said centering member at the side of said centering member facing the interior of said cylindrical electrode, and an equipotental cathode projecting from the outside into said centering member to face said control electrode, the position of said control electrode being secured by a lead wire passing through a slit of said centering member and fastened to the latter by meansof a glass bead.

3. A cathode ray tube comprising a cylindrical electrode, a ring-shaped centering member of insulating material, closely iitted in and supported by the one end of said cylindrical electrode, a disc-shaped control electrode mounted in a central recess of said centering member at the side of said centering member facing the interior of said cylindrical electrode, and an equipotential cathode projecting fr'om the outside into said centering member to face said control electrode, said cathode being carried by a supporting member fastened to said centering member by means of a glass bead, the position of said control electrode being secured by a leadwire passing through a slit of said centering member and fastened to the latter by means of a further glass bead, at least a part including said cylindrical electrode, said supporting member and said lead-in wire, of the elements of the electrode system of said tube being nxed to Supporting rods directly embedded in a. base plate of pressed glass forming the socket portion of the tube envelope.

4. A cathode ray tube as set forth in claim 3, wherein at least one of said supporting rods projects through said base plate and is formed to serve as a lead-in conductor.

5. A cathode ray tube comprising a cylindrical electrode, a ring-shaped centering member of insulating material, closely fitted in and supported by the one end of said cylindrical electrode, a disc-shaped control electrode mounted in a central recess of said centering member at the side of said centering member facing the interior of said cylindrical electrode, an equipotential cathode projecting from the outside into said centering member to face said control electrode, said cathode being carried by a supporting member fastened to said centering member by means of a glass bead, the position of said control electrode beingsecured by a lead-Wire passing through a slit of said centering member and fastened to the latter by means of a further glass bead, at least a part including said cylindrical electrode, said supporting member and said lead-in wire, of the elements of the electrode system of said tube being Xed to supporting rods directly embedded in a base plate of pressed glass forming the socket portion of the tube envelope, at least one of said supporting rods projecting through said base plate and being formed to serve as a lead-in conductor, and at least one additional lead-in rod directly embedded in and projecting through said base plate.

6. In a self-contained unitary electrode assembly for a cathode ray tube, a tubular cylindrical electrode, an apertured diaphragm mounted in said electrode adjacent to one end thereof, a ring-shaped centering member of insulating material having an outer diameter substantially the same as the inside diameter of said electrode and having substantially parallel side faces, said cen,- tering member being closely tted in said one end of the electrode with one side face adjacent to said diaphragm and With the major portion of the centering member extending from the electrode, a control diaphragm recessed into said centering member and positioned parallel to said apertured diaphragm, a cathodemounted in said centering member in axial alignment with said diaphragms and having an end face adjacent to said control diaphragm, and means supporting said electrode and said cathode in place.

KLEMENS OHL. 

